This invention relates to a transformer apparatus comprising a transformer unit insulated with insulating oil and a switch unit insulated with an insulating gas.
In many prior art transformer apparatus, different insulating fluids are used for the switch unit and for the transformer unit. The switch unit is usually insulated with air, insulating oil, SF.sub.6 gas, vacuum, etc., while the transformer unit is usually insulated with air, insulating oil, SF.sub.6 gas, etc. Recently, SF.sub.6 gas has been extensively used as the insulating fluid for the switch unit. On the other hand, in many cases the usual insulating oil is used as the insulating fluid for the transformer unit. For these reasons, a construction as shown in FIG. 1 is typically adopted in cases where the switch and transformer units are insulated with different insulating fluids. In the prior art transformer apparatus shown in FIG. 1, the transformer unit 5, which is insulated with sealed insulating oil 3, is disposed in a transformer tank 1A. A reservoir 12 is coupled to the transformer tank 1A. The switch unit 4 which is insulated with a sealed insulating gas 2 is disposed in a switch tank 1B. The transformer unit 5 and switch unit 4 are coupled together by a penetrating bushing 13 which provides a seal between both the tanks 1A and 1B. The switch unit 4 is connected to an aerial cable 9 through a primary side bushing 8. The transformer unit 5 is connected to an aerial side cable 11 through a secondary side bushing 10.
With the above construction, however, the penetrating bushing has a complicated and expensive construction. In addition, nitrogen (N.sub.2) gas must be sealed in the interior of the reservoir. This means that excess insulating oil corresponding in quantity to the oil in the reservoir is necessary. Further, both the tanks occupy a large floor space, so that a broad installation area is required. The fact that the occupied floor space is so large is also undesirable from the stand-point of transport.